The present invention relates to devices for controlling heating and cooling equipment for buildings and particularly relates to wall thermostats or temperature actuated switches for energizing and de-energizing electrically operated heating and cooling functions. Typically, devices of this type provide a means for sensing the temperature of the room or area of the building for which climatic control is desired; and, in response to sensing predetermined changes in temperature or a predetermined temperature level, actuate electrical switches which employ low voltage current for actuating relays to energize or de-energize line power heating or cooling functions such as resistance heaters or compressors for operating cooling systems and blowers for circulating heated or cooled air. Low voltage thermostats have been employed for many years in building temperature controls to minimize the amount of heavy current carrying wiring to connect the wall thermostats and controls to the centralized heating and cooling equipment. Low voltage thermostats also eliminated the need for providing line voltage electrical insulation, the controls actuated by the building occupants.
However, in recent times it has been found desirable in certain types of building construction to employ individual zone or room heating and cooling systems rather than a central heating or cooling system for the entire building. Where individual systems are employed for heating and cooling small areas such as a single room or a group of small rooms, as for example in apartments or condominiums, it has been found desirable and economical from a building construction standpoint to provide direct line voltage actuation of the heating and cooling system from the wall thermostat, as for example where electric heat pumps are employed. It has also been desirable to provide occupant actuated controls in combination with the thermostatically operated switches for controlling the heating and cooling system for the rooms or areas subject to climate control.
Furthermore, in order to realize economies of construction, it has been desirable to provide line voltage thermostats and system controls in a single width or "gang" electrical wall outlet box. This is particularly desirable in modern building construction wherein interior walls and partitions are fabricated using sheet metal wall studs and plaster board which is attached to the sheet metal studs by mechanical fastening techniques. Single width electrical outlets are desirable in such construction because of the minimum aperture required to be cut in the plaster board and the difficulty encountered in properly anchoring double width electrical outlet boxes to the combination of sheet metal studs and plaster board. Accordingly, it has been desirable to find a way or means of incorporating a line voltage wall thermostat including line voltage switches for fan control into a single width electrical wall outlet box.
It has further been desired to provide for mounting a line voltage thermostat including line voltage fan control switches on a single outlet wall box and to provide for proper electrical installation to minimize hazard from electrical shock and also to provide for resistance against external impact.
Where it is desired to provide line voltage current switching in a wall thermostat, it has been found advantageous to employ a bulb and capillary type temperature sensor because the expansion of the fluid in the bulb and capillary provides sufficient force acting against a diaphragm to enable actuation of a snap-acting switch capable of handling the desired current load at line voltage. However, in attempting to provide a wall thermostat employing a bulb-and-capillary temperature sensor, problems have been encountered in mounting such a device in an economical and adequately insulated manner on a single width electrical wall outlet box. Thus, it has been desired to provide an economical way or means of utilizing a bulb and capillary type temperature sensor for a line voltage wall thermostat combined with line voltage power switching for fan control and to provide such an assemblage in an insulated and protected enclosure for mounting on a single width electrical wall outlet box.